Fraunhofer Tests a New Underwater Energy Storage Concept

The Fraunhofer Institute is planning to test a new storage concept in a German lake before the end of this year. The storage idea, which involves placing hollow concrete globes on sea or lake beds, resembles an underwater balloon technology already developed by Ontario, Canada-based Hydrostor. In reality, the two concepts are quite different, however. While Hydrostor’s balloons use water pressure to deliver a novel form of compressed air energy storage (CAES), the Fraunhofer project, called StEnSEA (Stored Energy in the Sea), is essentially a variant of pumped hydro. “Instead of a lower and upper reservoir, the system uses a pressure tank as a lower reservoir placed on the seabed at 600 to 800 meters,” said Matthias Puchta, head of the Department of Energy Storage Systems within the Fraunhofer's energy process engineering division. “The water column above the entrance of t...